Telephone signaling system



. panying drawing is one Patented Oct. 23, 1928.

UNITED STATES PATENT OFFICE.

CHARLES S. DEMABEST,

OF RIDGEWOOD, NEW JERSEY,

lAND OWENv n. LoYNEs, or

BROOKLYN, NEW YORK, ASSIGNORS TO AMERICAN TELEPHONE AND TELEGBAPHCOMPANY, A CORPORATION OF NEW YORK.

TELEPHONE SIGNALING SYSTEM.

Application led May 19, 1923. Serial No. 110,250

This invention relates to telephone signaling systems, and moreparticularly to arrangements for transmitting supervisory signalsbetween central office stations.

In the operation of a group of telephone circuits by improved traiiicmethods, a. nurnber of supervisory signals are required. Facilities forthe transmission of these supervisory signals are sometimes notavailable, as in the case of radio speech channels; and, in the case ofwire circuits, they cannot always be obtained, unless there aresacrificed facilities for the transmission of Morse telegraph signalsover the telephone circuits. Furthermore, with the present standardfacilities for signaling over voice circuits, certain precautions mustbe taken in orden to guard against interference with the signals by thevoice currents and in order to reduce the interference from other voicecircuits and the interference caused in other voice circuits.

it is the object of applicants invention to transmit supervisory signalsin cases in which the facilities cannot be obtained by wire means, as inthe case of radio speech channels, and, in the case of Wire circuits, totransmit such signals without any sacriice ot Morse telegraph facilitiesand without anyv of the types ot interference mentioned above.

Applicants accomplish this object by transmitting all the supervisorysignals for a grou of voice circuits over a common radio c annel betweenthe central office stations.

The arrangement described below and illustrated diagrammatically in theaccomsuitable for transmitting by applicants means the signals employedin the so-called third wire method of operation, sometimes called thethird wire method of ring down operation, in which the signals aretransmitted from the toll line circuit to the toll cord associatedtherewith, over a third wire.

Fig. 1 shows diagrammatically and, in part, schematically, a group ofcircuits suitable for the practice of the invention. Fig. 1a showsdiagrammatically a detail of one of the cord circuits. It is to beunderstood that .this ligure is intended to show only the circuitchanges made by certain switching operations and is not to be taken asa.

there is required one radio representation of the actual structureinvolved. It is to be understood further that the corresponding detailof the cord circuit at the opposite end of the system is the same asthat shown 1n this ligure.

With reference to the accompanying drawing, station A is a telephonecentral office station connected with a distant central otiice station Bby a plurality of voice channels, which may be ordinary wire circuits,carricr circuits, or radio channels. The system is shown equipped foroperation in either direction, that is, for the initiation ot a call ateither station and the proper signaling and supervision at bothstations. The apparatus at each station consists essentially of radiotransmitting means, radio receiving means, and the following inassociation with each of the voice channels: means for producing radiosignaling current for transmission, means for suitably tuning thereceiving means, the usual annunciators, and means for associating thesignaling current producers and the annunciators with the radiotransmitting and receiving apparatus, respectively. For each voicechannel served signaling frequency for signaling in each direction, thesignaling current producer associated with that channel at each stationproducing an alternating current of a predetermined frequency and thereceiver at the other station being correspondingly tuned by the circuitassociated with that channel.

It is to be understood that only the apparatus associated with one voicechannel is shown in full, the apparatus peculiarly associated with theother channels being merely indicated and its connection to the radiotransmitting and receiving apparatus shown.

The details of the -signaling system will be clearly understood from thefollowing description of the ope-ration thereof.

If a subscriber directly connected with the central oiiice station Awishes to communicate with a subscriber connected to the dis.- tantcentral oiice station B, the operator at station A plugs -the toll cordinto the 'jack J. Battery from the sleeve of the toll cord operatesrelay C, which, in turn, operates relay D. The operator then rings, andground is placed over the lead T from the operators key equipment (seeFig. 1*), resulting in the operation of relay7 E. The

operation of relay E connects the oscillator O, which produces highfrequency signaling current, through the tuned circuit F as sociatedwith the voice channel under consideration and the common amplifier G tothe radio transmitting antenna of station A radio signal is received inthe receiving aliteniia at station B, is changed in frequency (anoscillator being associated with the frequency changer), and is passedthrough the common amplifier H', the timed circuit K associated with thevoice channel under con# sideiation, land the rectifier M to the relayN, which operates. The operation of relay N connects ground over a backcontact of relay D to the upper winding of relay P. Relay P operates,locks through its lower winding, and completes a circuit includingv thelamp L associated with the jack J The operator at station B, in responseto the lighting of the lamp L, plugs the toll cord into ack J. Batteryfrom the sleeve of this toll cord operates relay C', which, in turnoperates relay D. The operation of relay D breaks the locking circuit ofrelay P, releasing that relay, and extinguishes the lam L It) theoperator at station A reringson the circuit established as above, groundis again connected over lead T to relay E, and a second radio signal istransmitted to station B, re-operating relay N. Since relay D remainsoperated, this second operation of relayN connects ground throughthemake contact of relay D and the winding of relay S 'to the sleeve ofjack J. The relay S operates and locks in parallel with relay bothrelays being held operated by the battery from the sleeve of the tollcord inserted in the jack. The resistance of relay S is chosen to beconsiderably lower than that of relay C. Accordingly, when these tworelays are connected in parallel, as described above, the marginal relayin the sleeve ofthe toll cord will operate in a manner well understoodin the art lamp associated with the toll cord. When the operator atstation B answers and operates a talking key X (Fig. ll'in the tollcord, the resistance Y is switc ed in, and lthe Iresistance of the tollcord is sufficiently increased thereby to cause the release of relay S,relay C remaining operated. Consequently the 'marginal relay in the tollcord releases and extinguishes the supervisory lamp. When the toll cordsare removed from the jacks J and J at stations A and B, respectively,all the relays of the system are restored to the normal condition.

Only somuch of the toll cord circuits is shown as appears to benecessary toa full understandin of applicants invention.

The operation ofthe signaling system will now be described in connectionwith a call initiated` at station B. -The operator at staand light thesupervisory' tion B plugs a toll cord into the jack J',

causing the operation of relay C', which, I

in turn, causes the operation of relay D. When the operator rings,ground is placed over lead T to relay E', which operates. The operationof relay E connects the oscillator O', which roduces high frequencysignaling current, t rough the tuned circuit F and the common amplifierG to the radio transmitting antenna at station B. The radio signal istransmitted and received at the distant station A in the receivingantenna, is changed in frequency, and is passed through the commonamplifier H, the tuned circuit K, and the rectifier M to the relay N.This relay N operates and connects ground through a back contact ofrelay D to the lower winding of relay P. The relay P 0perates, locksthrough its upper windings, and completes a circuit includin the lamp Lassociated with the jack J, he lighting of this lamp directing theattention of the operator at station A to the call. The receivingoperator responds by plugging a toll cord into jack J, relay C, which,in turn, causes the operation of relay D. The operation of relay Dbreaks the locking circuit of relay P, releasing that relay, andextinguishes the lamp L.

If the operator at the originating station B rerings on the circuitestablished as described above, ground is again placed over lead T tothe relay E, which again operates, causing a second radio signal to betransmitted to station A, where relay N is re-operated. Since relay Dremains operated, the second operation of relay N connects groundthrough the make contact of relay D and the winding of relay S to thesleeve of jack J. Relay Soperates and locks 1n parallel with relay C,held operated by battery from the sleeve of the toll cord inserted injack J. The resistance of relay S is chosen lconsiderably lower thanthat of relay C. Accordingly, when these two relays are connected inparallel, the marginal relay in the sleeve of the bot-h relays beingtoll cord will operate, lighting the super-l visory lamp associated withthe .toll cord. When the operator at station A answers and operatesher/talking key in the toll cord, the resistancel of the toll cord issufficiently increased to result in the release of relay S, relay Cremaining operated. The release of relay S causes the release of themarginal relay in the sleeve of the toll cord, and accordinglyextinguishes the supervisory lamp.

While applicants invention has been disclosed in one specific embodimentwhich is deemed desirable, it is to be understood that it is capable ofembodiment in lmany other and dierent forms without a departure fromythe scope of the invention as defined in the appended claims.

What is claimed is:

causing the operation ofy 1. In a telephone system including two centraloffice stations and a voice channel connecting said stat-ions, means ateach station for generating and transmitting radio signals, means ateach station for receiving the radio signals transmitted from the otherstation, a first annunciator at each station, a second annunciator ateach station, automatic means at each station, responsive to ringingcurrent introduced at that station, for operating the signal generatingand transmitting means at that station, automatic means at `each stationfor operating the first annunciator at that station in response to aninitial radio signal received from the other station, and automaticmeans at each station for operating the second annunciator at thatstation in response to a subsequent radio signal received from the otherstation.

2. In a telephone system including two central otlice stations and avoice channel connecting said stations, means at each station forgenerating and transmitting radio signals, means at each station forreceiving the radio signals transmitted from the other station, a firstannunciator at each station,

a second annunciator at each station, automatic means at each station,responsive to ringing current introduced at that station, for operatingthe signal generating and transmitting means at that station, automaticmeans at each station for operating the first annunciator at thatstation in response to an initial radiorsignal received from the otherstation, automatic means at each station for operating the secondannunciator at that station in response to a subsequent radio signalreceived from the other station, and automatic means at each station forpreventing the re-operation of the first annunciator at that station inresponse to said subsequent radio signal received from the otherstation.

3. In a telephone system includin two central oiiice stations and aplurality o voice channels connecting said stations, means at eachstation for transmitting radio signals, means at each station forreceiving radio si fnals, and at each station in association wit eachvoice channel the following; means for producing signaling current of afrequency peculiar to that station and to that voice channel, means fortuning the to an initial radio signal, of the pre eter mined frequency,received from the other station, and automatic means for operating thesecond annunciator at that station in response to a subsequent radiosignal, of the predetermined frequency, received from the other station.

4. In a telephone system includi two central oice stations and aplurality o voice channels connecting` said stations, means at eachstation for transmitting radio signals, means at each station forreceiving radio signals, and at each station in association with eachvoice channel the following: means for producing signaling current of afrequency peculiar to that station and to that voice channel, means fortuning the signal receiving means at that station to the peculiarfrequency produced at the other station and corresponding to that voicechannel, a first annunciator, a second annunciator, automatic means,responsive to ringing current produced at that station, for connectingsaid current producing means to the radio signal transmitting means atthat station, annunciator at that station in response to an initialradio signal, 4of the predetermined frequency, received from the otherstation, automatic means for operatingthe second annunciator at thatstation in response to a sub uent radio signal, of the redeterminedrequency, received from t e other station, and automatic means forpreventing the reoperation of the first annunciator at that station inresponse to said subsequent radio signal received from the otherstation.

In testimony whereof, we have signed our names to this specificationthis 18th day of May 1926.

CHARLES S. DEMARE-ST. OWEN H. LOYNES.

automatic means for operating the first

